Hydrogen clathrate

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A hydrogen clathrate is a clathrate containing hydrogen in a water lattice. This substance is interesting due to its possible use to store hydrogen in a hydrogen economy. [1] [2] A recent review that accounts the state-of-the-art and future prospects and challenges of hydrogen storage as clathrate hydrates is reported by Veluswamy et al. (2014). [3] Another unusual characteristic is that multiple hydrogen molecules can occur at each cage site in the ice, one of only a very few guest molecule that forms clathrates with this property. The maximum ratio of hydrogen to water is 6 H2 to 17 H2O. [4] It can be formed at 250K in a diamond anvil at a pressure of 300MPa (3000 Bars). It takes about 30 minutes to form, so this method is impractical for rapid manufacture. [5] The percent of weight of hydrogen is 3.77%. [4] The cage compartments are hexakaidecahedral and hold from two to four molecules of hydrogen. At temperatures above 160K the molecules rotate around inside the cage. Below 120K the molecules stop racing around the cage, and below 50K are locked into a fixed position. This was determined with deuterium in a neutron scattering experiment. [4]

Under higher pressures a 1:1 ratio clathrate can form. It crystallises in a cubic structure, where H2 and H2O are both arranged in a diamond lattice. It is stable above 2.3 GPa. [6]

Under even higher pressures (over 38 GPa) there is a prediction of the existence of a clathrate with a cubic structure and a 1:2 ratio: 2H2•H2O. [7]

More complex clathrates can occur with hydrogen, water and other molecules such as methane, [8] and tetrahydrofuran. [9]

Since hydrogen and water ice are common constituents of the universe, it is very likely that under the right circumstances natural hydrogen clathrates will be formed. This could occur in icy moons for example. [8] Hydrogen clathrate was likely to be formed in the high pressure nebulae that formed the gas giants, but not to have formed in comets. [10]

Related Research Articles

In chemistry, hydronium (hydroxonium in traditional British English) is the cation [H3O]+, also written as H3O+, the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid is dissolved in water, as Arrhenius acid molecules in solution give up a proton (a positive hydrogen ion, H+) to the surrounding water molecules (H2O). In fact, acids must be surrounded by more than a single water molecule in order to ionize, yielding aqueous H+ and conjugate base. Three main structures for the aqueous proton have garnered experimental support: the Eigen cation, which is a tetrahydrate, H3O+(H2O)3, the Zundel cation, which is a symmetric dihydrate, H+(H2O)2, and the Stoyanov cation, an expanded Zundel cation, which is a hexahydrate: H+(H2O)2(H2O)4. Spectroscopic evidence from well-defined IR spectra overwhelmingly supports the Stoyanov cation as the predominant form. For this reason, it has been suggested that wherever possible, the symbol H+(aq) should be used instead of the hydronium ion.

<span class="mw-page-title-main">Methane clathrate</span> Methane-water lattice compound

Methane clathrate (CH4·5.75H2O) or (4CH4·23H2O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice. Originally thought to occur only in the outer regions of the Solar System, where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under sediments on the ocean floors of the Earth (approx. 1100m below the sea level). Methane hydrate is formed when hydrogen-bonded water and methane gas come into contact at high pressures and low temperatures in oceans.

<span class="mw-page-title-main">Clathrate hydrate</span> Crystalline solid containing molecules caged in a lattice of frozen water

Clathrate hydrates, or gas hydrates, clathrates, or hydrates, are crystalline water-based solids physically resembling ice, in which small non-polar molecules or polar molecules with large hydrophobic moieties are trapped inside "cages" of hydrogen bonded, frozen water molecules. In other words, clathrate hydrates are clathrate compounds in which the host molecule is water and the guest molecule is typically a gas or liquid. Without the support of the trapped molecules, the lattice structure of hydrate clathrates would collapse into conventional ice crystal structure or liquid water. Most low molecular weight gases, including O2, H2, N2, CO2, CH4, H2S, Ar, Kr, and Xe, as well as some higher hydrocarbons and freons, will form hydrates at suitable temperatures and pressures. Clathrate hydrates are not officially chemical compounds, as the enclathrated guest molecules are never bonded to the lattice. The formation and decomposition of clathrate hydrates are first order phase transitions, not chemical reactions. Their detailed formation and decomposition mechanisms on a molecular level are still not well understood. Clathrate hydrates were first documented in 1810 by Sir Humphry Davy who found that water was a primary component of what was earlier thought to be solidified chlorine.

In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understood.

In chemistry, noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon.

<span class="mw-page-title-main">Clathrate compound</span> Chemical substance consisting of a lattice that traps or contains molecules

A clathrate is a chemical substance consisting of a lattice that traps or contains molecules. The word clathrate is derived from the Latin clathratus, meaning 'with bars, latticed'. Most clathrate compounds are polymeric and completely envelop the guest molecule, but in modern usage clathrates also include host–guest complexes and inclusion compounds. According to IUPAC, clathrates are inclusion compounds "in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules." The term refers to many molecular hosts, including calixarenes and cyclodextrins and even some inorganic polymers such as zeolites.

Carbon dioxide hydrate or carbon dioxide clathrate is a snow-like crystalline substance composed of water ice and carbon dioxide. It normally is a Type I gas clathrate. There has also been some experimental evidence for the development of a metastable Type II phase at a temperature near the ice melting point. The clathrate can exist below 283K (10 °C) at a range of pressures of carbon dioxide. CO2 hydrates are widely studied around the world due to their promising prospects of carbon dioxide capture from flue gas and fuel gas streams relevant to post-combustion and pre-combustion capture. It is also quite likely to be important on Mars due to the presence of carbon dioxide and ice at low temperatures.

<span class="mw-page-title-main">Ho-Kwang Mao</span> Chinese-American geologist

Ho-Kwang (Dave) Mao is a Chinese-American geologist. He is the director of the Center for High Pressure Science and Technology Advanced Research in Shanghai, China. He was a staff scientist at Geophysical Laboratory of the Carnegie Institution for Science for more than 30 years. Mao is a recognized leading scientist in high pressure geosciences and physical science. There are two minerals named after him, Davemaoite and Maohokite.

<span class="mw-page-title-main">Magnesium hydride</span> Chemical compound

Magnesium hydride is the chemical compound with the molecular formula MgH2. It contains 7.66% by weight of hydrogen and has been studied as a potential hydrogen storage medium.

Solid hydrogen is the solid state of the element hydrogen, achieved by decreasing the temperature below hydrogen's melting point of 14.01 K. It was collected for the first time by James Dewar in 1899 and published with the title "Sur la solidification de l'hydrogène" in the Annales de Chimie et de Physique, 7th series, vol. 18, Oct. 1899. Solid hydrogen has a density of 0.086 g/cm3 making it one of the lowest-density solids.

A Bjerrum defect is a crystallographic defect which is specific to ice, and which is partly responsible for the electrical properties of ice. It was first proposed by Niels Bjerrum in 1952 in order to explain the electrical polarization of ice in an electric field. A hydrogen bond normally has one proton, but a hydrogen bond with a Bjerrum defect will have either two protons or no proton. D-defects are more energetically favorable than L-defects. The unfavorable defect strain is resolved when a water molecule pivots about an oxygen atom to produce hydrogen bonds with single protons. Dislocations of ice Ih along a slip plane create pairs of Bjerrum defects, one D defect and one L defect.

Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly considered that helium compounds cannot exist at all, or at least under normal conditions. Helium's first ionization energy of 24.57 eV is the highest of any element. Helium has a complete shell of electrons, and in this form the atom does not readily accept any extra electrons nor join with anything to make covalent compounds. The electron affinity is 0.080 eV, which is very close to zero. The helium atom is small with the radius of the outer electron shell at 0.29 Å. Helium is a very hard atom with a Pearson hardness of 12.3 eV. It has the lowest polarizability of any kind of atom, however, very weak van der Waals forces exist between helium and other atoms. This force may exceed repulsive forces, so at extremely low temperatures helium may form van der Waals molecules. Helium has the lowest boiling point of any known substance.

<span class="mw-page-title-main">Dioxidanylium</span> Ion

Dioxidanylium, which is protonated molecular oxygen, or just protonated oxygen, is an ion with formula HO+
2. It is formed when hydrogen containing substances combust, and exists in the ionosphere, and in plasmas that contain oxygen and hydrogen. Oxidation by O2 in superacids could be by way of the production of protonated molecular oxygen.

<span class="mw-page-title-main">Solid nitrogen</span> Solid form of the 7th element

Solid nitrogen is a number of solid forms of the element nitrogen, first observed in 1884. Solid nitrogen is mainly the subject of academic research, but low-temperature, low-pressure solid nitrogen is a substantial component of bodies in the outer Solar System and high-temperature, high-pressure solid nitrogen is a powerful explosive, with higher energy density than any other non-nuclear material.

Nitrogen clathrate or nitrogen hydrate is a clathrate consisting of ice with regular crystalline cavities that contain nitrogen molecules. Nitrogen clathrate is a variety of air hydrates. It occurs naturally in ice caps on Earth, and is believed to be important in the outer Solar System on moons such as Titan and Triton which have a cold nitrogen atmosphere.

Russell Julian Hemley is an American geophysicist, solid-state physicist, and physical chemist. Hemley is especially notable for his work in the theoretical prediction and experimental observation of near room-temperature superconductivity in lanthanum decahydride under high pressure.

A polyhydride or superhydride is a compound that contains an abnormally large amount of hydrogen. This can be described as high hydrogen stoichiometry. Examples include iron pentahydride FeH5, LiH6, and LiH7. By contrast, the more well known lithium hydride only has one hydrogen atom.

Lanthanum decahydride is a polyhydride or superhydride compound of lanthanum and hydrogen (LaH10) that has shown evidence of being a high-temperature superconductor. It was the first metal superhydride to be theoretically predicted, synthesized, and experimentally confirmed to superconduct at near room-temperatures. It has a superconducting transition temperature TC around 250 K (−23 °C; −10 °F) at a pressure of 150 gigapascals (22×10^6 psi), and its synthesis required pressures above approximately 160 gigapascals (23×10^6 psi).

Metallization pressure is the pressure required for a non-metallic chemical element to become a metal. Every material is predicted to turn into a metal if the pressure is high enough, and temperature low enough. Some of these pressures are beyond the reach of diamond anvil cells, and are thus theoretical predictions. Neon has the highest metallization pressure for any element.

<span class="mw-page-title-main">Wendy Mao</span> Chinese American geologist

Wendy Li-Wen Mao is an American geologist who is a professor at SLAC National Accelerator Laboratory. Her research considers the mineral physics of planetary interiors, new materials under extreme environments and novel characterisation techniques. In 2021 she was elected Fellow of the European Association of Geochemistry.

References

  1. ↑ Hirscher, Michael (4 August 2010). "Clathrate Hydrates". Chapter 3. Clathrate Hydrates. Wiley. pp. 63–79. doi:10.1002/9783527629800.ch3. ISBN   9783527629800.{{cite book}}: |work= ignored (help)
  2. ↑ Sabo, Dubravko; Sabo, Dubravko; Clawson, Jacalyn; Rempe, Susan; Greathouse, Jeffery; Martin, Marcus; Leung, Kevin; Varma, Sameer; Cygan, Randall; Alam, Todd (7 March 2007). "Hydrogen clathrate hydrates as a potential hydrogen storage material". MAR07 Meeting of the American Physical Society. 52 (1): S39.012. Bibcode:2007APS..MARS39012S . Retrieved 10 September 2011.
  3. ↑ Veluswamy, Hari Prakash; Kumar, Rajnish; Linga, Praveen (2014). "Hydrogen storage in clathrate hydrates: Current state of the art and future directions". Applied Energy. 122: 112–132. Bibcode:2014ApEn..122..112V. doi:10.1016/j.apenergy.2014.01.063.
  4. 1 2 3 Lokshin, Konstantin A.; Yusheng Zhao; Duanwei He; Wendy L. Mao; Ho-Kwang Mao; Russell J. Hemley; Maxim V. Lobanov & Martha Greenblatt (14 September 2004). "Structure and Dynamics of Hydrogen Molecules in the Novel Clathrate Hydrate by High Pressure Neutron Diffraction". Physical Review Letters. 93 (12): 125503–1–125503–4. Bibcode:2004PhRvL..93l5503L. doi:10.1103/PhysRevLett.93.125503. PMID   15447276.
  5. ↑ Mao, Wendy L.; Mao, A. F. Goncharov; V. V. Struzhkin; Q. Guo; J. Hu, J. Shu; R. J. Hemley; M Somayazulu & Y. Zhao (2002). "Hydrogen Clusters in Clathratehydrate". Science. 297 (5590): 2247–2249. Bibcode:2002Sci...297.2247M. doi:10.1126/science.1075394. PMID   12351785. S2CID   24168225.
  6. ↑ Vos, Willem L.; Finger, Larry W.; Hemley, Russell J.; Mao, Ho-kwang (August 1996). "Pressure dependence of hydrogen bonding in a novel H2O-H2 clathrate". Chemical Physics Letters. 257 (5–6): 524–530. Bibcode:1996CPL...257..524V. doi:10.1016/0009-2614(96)00583-0.
  7. ↑ Qian, Guang-Rui; Lyakhov, Andriy O.; Zhu, Qiang; Oganov, Artem R.; Dong, Xiao (8 July 2014). "Novel Hydrogen Hydrate Structures under Pressure". Scientific Reports. 4: 5606. Bibcode:2014NatSR...4E5606Q. doi:10.1038/srep05606. PMC   4085642 . PMID   25001502.
  8. 1 2 Struzhkin, Viktor; Burkhard Militzer; Wendy L. Mao; Ho-kwang Mao & Russell J. Hemley (7 December 2006). "Hydrogen Storage in Molecular Clathrates" (PDF). Chem Rev. 107 (10): 4133–4151. doi:10.1021/cr050183d. PMID   17850164.
  9. ↑ Smirnov, G. S.; Stegailov, V. V. (17 December 2015). "Anomalous diffusion of guest molecules in hydrogen gas hydrates". High Temperature. 53 (6): 829–836. doi:10.1134/S0018151X15060188. S2CID   123843390.
  10. ↑ Lunine, Jonathan I.; Stevenson, David J. (1985). "Thermodynamics of clathrate hydrate at low and high pressures with application to the outer solar system". The Astrophysical Journal Supplement Series. 58: 493. Bibcode:1985ApJS...58..493L. doi:10.1086/191050 . Retrieved 10 September 2011.
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